All immersed structures, for example bridge pillars, dikes, dams or offshore drilling platforms, are subject to the effects of corrosion in the longer or shorter term. Such effects tell in particular on all the metal parts immersed in a marine environment and, depending on the extent of the corrosion, they often result in mechanical weakening of the entire structure. The strength and lifetime of the structure are accordingly reduced.
The anticorrosion treatments which have been carried out hitherto use quasi-manual techniques. The most widely practiced solution in fact consists in utilizing the services of divers, who, under several meters or tens of meters of water, manually coat the elements to be treated with, for example, paints, resins or mastics. Such techniques, practiced under difficult conditions, are very expensive, hazardous for the workforce and, most frequently, rather unsatisfactory in terms of their effectiveness.
In addition to the adverse effects due to corrosion, immersed structures of this kind suffer the consequences of various mechanical stresses such as, for example, gravity, the repeated impact of the waves, the pressure of underwater currents or the traction on anchorage points. Offshore drilling platforms are relatively sensitive structures in this respect, by virtue of both their construction and their exposure to the natural elements. Under the effect of the swell over a prolonged period, constituent elements such as branch joints are continually subjected to forces of traction, compression or even shear or torsion. Since they generally contain a large number of welds, these branch joints constitute weak points which should be checked regularly, protected or even reinforced if necessary, these operations being difficult, if not dangerous, at very great depths.
Although simulations on mock-ups or with the aid of theoretical models are possible and enable the weakest points of such structures to be identified beforehand if necessary, the number and variety of the effects to which branch joints of immersed drilling platforms may be subject are such that, in practice, one has to make do with taking action a posteriori, i.e. when the structure is already in service, after a more or less prolonged period of immersion.
To carry out the rigid assembly or mechanical reinforcement and the anticorrosion treatment of elements forming part of immersed structures, such as branch joints, for example, it is essential for those skilled in the art to have at their disposal technical solutions which are easily applicable, non-hazardous and reliable. This is advantageously achieved by using the device and following the installation procedure set forth herein.